This invention relates to methods and apparatus for surface treatment of powdered materials for easier dispersion of the powdered material in fluids.
When powder is dispersed in fluids, especially in liquids, for example when pigment is dispersed in resin varnish, where the fluid is generally referred to herein as the "carrier" or "vehicle", low affinity of the powder for the fluid adversely affects dispersion of the powder throughout the fluid. It is therefore necessary to improve affinity of the powder for the fluid by surface treatment of the powder.
Dry surface treatment of powder has a number of advantages, such as being a simple process. As an example, see the method of treating surfaces of organic pigments with low temperature plasma and of dispersing pigments in resin having polar groups and/or a polar solvent as disclosed in Japanese Patent Application No. 58-217559, laid open to the public.
For surface treatment of powder using the low-temperature plasma method to be fully successful, however, improvements in the apparatus and in the productivity of the process are problems to be solved--these require getting both satisfactory contact efficiency and uniformity between the plasma and the powder being treated.